With current techniques, the formation factor is obtained by means of laboratory measurements on reservoir cores. These methods are expensive because of the cost of the coring operation and of the measurement itself, and the results are available only several months after drilling.
Acquisition of the experimental conductivity measurements on cores is based on a conventional material used in most petrophysics laboratories, and already implemented for example in patent FR-2,781,573 (U.S. Pat. No. 6,229,312) filed by the applicant, or in the following publication:                Sprunt, E. S., Maute, R. E., Rackers, C. I.: “An Interpretation of the SCA Electrical Resistivity”, The Log Analyst, pp. 76-88, March-April 1990.        
In order to overcome the high cost problem and the relatively long time required to obtain a measurement, techniques of calculating the formation factor from drill cuttings were developed. For example, U.S. Pat. No. 2,583,284 describes various methods for determining the formation factor from conductivity measurements carried out on drill cuttings. However, these techniques are very restricting on an experimental plane and the measurements relatively long to obtain.